Do bottlenose dolphins recognise themselves in a mirror?

My name is Alina Loth and I am doing my PhD at the University of St Andrews. In my thesis I focus on bottlenose dolphin communication and cognition. How do they use and perceive sounds in their communication, how do they learn, and which mental processes are they capable of? In the part of my research I present here, I am interested in whether or not dolphins recognise themselves in a mirror.


Every morning I force myself out of bed, drag my sleepy body to the bathroom and look at the mirror. Who is that human female with messy hair and sleepy eyes? And every morning, no matter how dishevelled I look, it is painfully obvious to me that, yep, I will have to wash her, and comb her – because that woman in the mirror is my own reflection. What seems like a normal morning routine happening in millions of bathrooms around the world is actually an amazing skill: Between the age of 15 and 24 months, human children start to realise that a mirror image is a reflection of themselves and not a second child behind glass. Even more astonishing, humans use mirrors as a tool to manipulate their appearance!

The ability for mirror self-recognition is thought to be an important step in the development of self-awareness and consciousness. But humans are not the only species able to recognise their reflection: Researchers developed the mirror mark test, a method to test animals for mirror self-recognition and most great ape species, Asian elephants and magpies already passed this test convincingly!

How does this test work? First of all the animals become accustomed to the presence of a mirror in their environment. Initially, most animals will exhibit social behaviours in front of the mirror that are comparable to what they would show when confronted with an unfamiliar conspecific – such as fear, aggression or play behaviour. After they have experienced the mirror for a while, some animals start to explore their own body by using the reflection, or they move rhythmically as if testing how they can manipulate the reflections (humans for example often wave their hand!). Other animals, for example dogs, never make it to a step where they show such self-directed behaviours.

This is when the actual mark test takes place. The animal gets a colour marking that it can’t see without the mirror (e.g. on their eyebrow or ear). An animal passes the test when it looks at its reflection and touches the marking on its body. Touching and manipulating the marking while checking the reflection is thought to show that the individual established a mental connection between the mirror reflection and its own body – simply speaking, they understand that they are seeing themselves.

Dolphins have many advanced cognitive skills, so researchers always suspected that they might also be able to recognise themselves in a mirror. But their body is so streamlined and adapted to the aquatic environment that they can’t touch a marking on their own body. Therefore we marked them around their eyes to see whether or not they would turn their body towards the yellow marked body side.

Did dolphins pass the test? Well, the tested dolphins did interact much more with their mirror reflection when they were marked yellow. However, they did not turn their bodies towards the marking. So apparently a yellow marked dolphin looks silly enough to stare at – but the dolphins didn’t figure out that they can check out the markings in greater detail or longer when they turn their bodies to the respective side.




Contact the researcher and illustrator

Alina Loth, PhD candidate